Strange one commuting home last night. I'm almost home, into Duddingston, in the 20mph zone, easily doing 20, and a car overtakes me, probably doing about 30. Natural reaction these days is for me to simply remakr 'Twenty'. Not shouted, not aggressive, just makes me feel better.
Driver's window was down, he heard me, slowed so that I came along his inside (so yes, he was therefore driving down the centre of the road with parked cars on either side and speed bumps) and shouted "What was that?" - thing is, it didn't sound aggressive at all, so I shouted back "Twenty miles an hour!". Again, not aggressive, merely informative.
He slows, tucks in behind me, but not tailgating, which I'd expected, and patiently follows me down to the next lights (where another car is already waiting, so he's not held up at all by slowing) and I turn off, and that's it.
Seems he genuinely didn't realise it was a 20 zone. Okay, so he should be paying attention, but in all honesty it was a strangely easy-going interaction (all conducted on the move).